Crane flies are a common sight, often appearing as large, gangly insects similar to an oversized mosquito. They frequently prompt questions about their environmental impact. Understanding their life cycle and behaviors reveals their functions within ecosystems. This article clarifies the role crane flies play, from their adult stage to their larval development, and addresses common concerns people have about them.
Identifying Crane Flies and Dispelling Common Myths
Crane flies are distinct insects characterized by their long, slender legs, elongated bodies, and a single pair of wings. They often appear brown or grey and can range significantly in size, with some species reaching a wingspan of up to 2.5 inches. A distinguishing feature is a V-shaped groove on their thorax, the body section behind their head. Their flight is weak and wavering, and their delicate legs break off easily.
Many people mistake crane flies for large mosquitoes, mistaking them for biters or blood-feeders. However, adult crane flies lack piercing mouthparts to bite humans or animals. They are also incorrectly called “mosquito hawks” or “skeeter-eaters,” but they do not prey on mosquitoes or other insects. Their mouthparts are snout-like, and many species do not feed as adults.
The Ecological Role of Crane Flies
Adult crane flies have a short lifespan, lasting only a few days to two weeks. Their primary purpose is reproduction. Many species do not feed as adults, while others consume only nectar and water. Their limited feeding means minor pollination contribution compared to other insects.
Crane flies’ ecological contributions come from their larval stage, often called “leatherjackets” due to their tough skin. These larvae are detritivores, feeding on decaying organic matter in diverse environments. They consume leaf litter, rotting wood, fungi, and algae in moist soil or aquatic habitats. Through this feeding, crane fly larvae play a role in nutrient cycling and the decomposition of organic material, aiding in soil health.
While most crane fly species are beneficial decomposers, a few species can have a different impact. For example, the larvae of the European crane fly (Tipula paludosa) and marsh crane fly (Tipula oleracea) feed on turfgrass roots and certain crops. This can lead to thinning turf or patchy brown areas, especially in lawns or agricultural fields. Damage occurs under specific conditions, like high larval populations, and is not characteristic of most crane fly species.
Addressing Crane Fly Nuisance
Crane flies can be a nuisance, when large numbers are attracted to outdoor lights and enter homes. Their clumsy indoor flight, bumping into objects, can be unsettling. However, adult crane flies are harmless to humans and do not bite or transmit diseases.
Concerns also arise from crane fly larvae, or leatherjackets, when their feeding on grass roots visibly damages lawns. If a lawn shows thinning or brown patches with high larval density (around 25-30 per square foot), management might be considered. Rather than chemical treatments, improving lawn health can mitigate damage. Proper watering, fertilization, aeration, and dethatching make the lawn less hospitable to larvae and help grass recover. Severe infestations requiring intervention are uncommon, and natural predators like birds and ground beetles help control larval populations.